Daniel Radcliffe's Harry Potter had an invisibility cloak unlike the devices made of metamaterials.

EXPERT'S RESPONSE

David R. Smith, a metamaterials expert at Duke University, comments on the invisibility devices in an e-mail to Dan Vergano:

"Although virtually all of the community now accepts the reality of negative index materials at low frequencies, there has been an ongoing discussion about whether negative index materials can be practically realized at telecommunications or visible wavelengths. Although there has been excellent work over the last several years in terms of designing metamaterials for those wavelengths, there has not been a single demonstration that suggests a usable material could be formed. Losses tend to rise as the frequency increases, to the point that optical metamaterials are so absorptive they would normally be considered opaque. The results by Zhang's group show that optical metamaterials may be more feasible than we have thought! With extremely careful design and nano-fabrication, they have succeeded in making what are, to my knowledge, the very first 'bulk' negative index metamaterials at telecommunications and visible wavelengths....

"So, while neither of these experiments addresses optical cloaking directly, they do show that the tools are being expanded and refined. Our ability to realize unique devices like optical cloaks or perfect lenses is directly related to our ability to design and fabricate higher quality metamaterials. The results by Zhang's group are two of the cleanest sets of measurements yet presented, and, in my opinion, represent a very significant step in the evolution of metamaterials."

The microscopic devices aren't actually in a cloak at this point, but they do bend light around their surfaces, researchers headed by Xiang Zhang of the University of California-Berkeley say. The devices rely on metamaterials, specially structured materials that in these cases have surfaces dotted with holes smaller than the width of visible light waves, less than 0.00003 of an inch across, which smoothly shuttle light rays around them.

"Being able to bend light in unusual ways is important for applications that almost resemble magic," physicist Ulf Leonhardt of Scotland's University of St. Andrews, who was not part of the prototype teams, writes in an e-mail. "There still is a long way to go, but the Berkeley team made an important step."

The field has been a hot area of study. Invisibility devices up till now have involved metamaterial devices that were "invisible" only from one angle or to microwaves but not visible light.

One of the new prototypes is a woven fishnet of silver nanowires, each one about 10,000 times thinner than a human hair. It was reported this week in the journal Science.

The team tested the device for red, or visible, light and infrared light and said the prototype bends red light from all angles hundreds of times more effectively than in past attempts.

The other device, reported this week in Nature magazine, relies on 21 stacked grids of silver and magnesium fluoride of similarly small sizes. The researchers found that the device bent infrared light around the grids.

Applications for invisibility devices extend beyond shielding oneself for an escape from a wizards academy. Shielding lenses from unwanted light frequencies would improve camera function, for example, and antennas invisible to noisy electromagnetic waves would fine-tune cellphone and radio communications.

And unlike Harry Potter's cloak, these fragile metamaterials would be blown away by the gentlest breeze.

"Developing a way to manufacture these materials on a large scale will also be a challenge," the researchers said in a university statement.

To report corrections and clarifications, contact Reader Editor Brent Jones. For publication consideration in the newspaper, send comments to letters@usatoday.com. Include name, phone number, city and state for verification.

Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more.